The disclosure of Japanese Patent Application No. 2001-102322 filed on Mar. 30, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates generally to a cylindrical elastic mount in which an inner shaft member and an outer sleeve member are elastically connected with each other by an elastic body interposed therebetween, and include flange portions formed at respective ones of axially opposite end portions thereof such that the flange portions are opposed to each other in an axial direction of the cylindrical elastic mount via the elastic body interposed therebetween. More particularly, the present invention is concerned with such a cylindrical elastic mount suitable for use in an automotive vehicle as a member mount, a deferential mount, a body mount and other connecting members, and a vibration isolating connector or a cylindrical elastic mount assembly including the cylindrical elastic mount as a component.
2. Description of the Related Art
A cylindrical elastic mount is known as one type of an vibration isolating connector interposed between two members of a vibration system. A member mount is one example of the cylindrical elastic mount, and is disposed between a sub-flame, e.g., a suspension member and a cross member, and a body of the vehicle for elastically supporting the sub-flame on the body in a vibration-isolating fashion. Such a known cylindrical elastic mount generally includes an inner metal sleeve and an outer metal sleeve, which are disposed in co-axial relation with each other and elastically connected with each other by a rubber elastic body interposed therebetween, and is installed between two members of the vibration system such that the outer metal sleeve is press-fitted into a fixing bore formed in one of the two members and the inner metal sleeve is fixedly assembled with a rod member formed in the other member and extending through its bore.
The known cylindrical elastic mount is required not only to exhibit a vibration damping or isolating effect with respect to a vibrational load applied thereto in an axial direction thereof from the suspension member and a power unit of the vehicle, but also to provide a stopper function for restricting an amount of displacement of the inner and outer metal sleeves relative to each other in a shock absorbing manner, upon application of a relatively large vibrational load to the cylindrical elastic mount.
For enabling the cylindrical elastic mount to exhibit the required high vibration isolating characteristics with respect to the vibrational load applied thereto in the axial direction, it is effective to arrange the cylindrical elastic mount so as to exhibit linear low spring characteristics within a large stroke range when the inner and outer metal sleeves are displaced relative to each other in the axial direction. Likewise, for enabling the cylindrical elastic mount to provide an excellent stopper function, it is effective to arrange the cylindrical elastic mount so as to exhibit non-linear spring characteristics wherein an axial spring constant of the rubber elastic body is smoothly increased.
Examples of the conventional member mounts are disclosed in JP-A-2000-61434, JP-B-2981598 and JP-A-210406, wherein the inner and outer metal sleeves have integrally formed flange portions, respectively, which are opposed to each other in the axial direction with the rubber elastic body interposed therebetween. When the inner and outer metal sleeves are displaced relative to each other in the axial direction, the elastic body interposed between the flange portions of the inner and outer sleeve members is accordingly compressed by and between the flange portions in the axial direction substantially entirely. Therefore, the conventional cylindrical elastic mount is likely to exhibit spring characteristics, i.e., load-deflection characteristics such that a low load region assuring a linear change of a low spring constant is narrowed, and the spring constant of the cylindrical elastic mount is skyrocketed in a high load region outside the low load region. Thus, the conventional member mount experiences an abrupt change of its spring constant when a relatively high vibrational load is applied thereto, and therefore is not able to sufficiently exhibit the vibration isolating capability with respect to the vibrational load applied thereto in the axial direction, and a shock absorbing capability upon application of the relatively large vibrational load thereto in the axial direction.
It is therefore an object of the invention to provide a cylindrical elastic mount which is novel in construction, and which is capable exhibiting an improved axial vibration isolating capability with the help of spring characteristics of the cylindrical elastic mount wherein a low load region permitting the cylindrical elastic mount to exhibit linear spring characteristics is extended, while being capable of restricting an axial displacement of an inner and outer metal sleeve relative to each other in a shock absorbing manner with the held of the spring characteristics of the cylindrical elastic mount wherein the spring constant of the cylindrical elastic mount is smoothly increased upon application of a relatively large vibrational load to the cylindrical elastic mount.
The above and/or optional objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A cylindrical elastic mount comprising: (a) an inner shaft member having an integrally formed flange portion extending radially outwardly from one of axially opposite ends thereof; (b) an outer sleeve member disposed around the inner shaft member with a radial spacing therebetween, the outer sleeve member having an integrally formed flange portion extending radially outwardly from one of axially opposite ends thereof corresponding to the one of axially opposite ends of the inner shaft member so that the flange portions of the inner shaft member and the outer sleeve member are opposed to each other in an axial direction parallel to a central axis of said cylindrical elastic mount with a given axial spacing between respective opposite surfaces of said flange portions; and (c) an elastic body disposed in the radial spacing between the inner shaft member and the outer sleeve member and in the axial spacing between the flange portions for elastically connecting the inner shaft member and the outer sleeve member; wherein the opposite surfaces of the flange portions of the inner shaft member and the outer sleeve member include respective tapered surfaces, which extend approximately parallel to each other in an axially outward direction inclined to the central axis, and are elastically connected with each other via the elastic body interposed therebetween.
In the cylindrical elastic mount constructed according to this mode of the invention, the flange portions of the inner shaft member and the outer sleeve member are opposed to each other in the direction inclined to the central axis of the cylindrical member at respective tapered surfaces of the opposite surfaces thereof. An axial vibrational load applied between the inner shaft member and the outer sleeve member acts on the flange portions and a part of the elastic body interposed between the flange portions in a direction inclined to the direction in which the tapered surface are opposed to each other and the elastic body has a thickness. Therefore, the applied axial vibrational load may act on the elastic body interposed between the tapered surfaces of the flange portions as components in a shear direction and a compression direction.
In the conventional elastic mount, since the opposite surfaces of the flange portions extend in the radial direction perpendicular to the central axis thereof, the elastic body interposed between the opposite surfaces of the flange portions is inevitably entirely subjected to compressive deformation upon application of the axial vibrational load thereto, eventually suffering from difficulty in exhibiting low spring characteristics over a wide load range and exhibiting moderate increase of the spring constant in a relatively high load region, as discussed above. In comparison with this conventional cylindrical elastic mount, the present cylindrical elastic mount is able to exhibit low spring characteristics of the elastic body with respect to axial vibrational loads, in accordance with the angle of incline of the tapered surfaces of the flange portions of the inner shaft member and the outer sleeve member to the central axis of the cylindrical elastic mount. As a result, the present cylindrical elastic mount permits the inner shaft member and the outer sleeve member to displace relative to each other over an enlarged axial distance without causing an abrupt increase of the spring constant of the elastic body. In other words, the present cylindrical elastic mount permits a relatively large stroke length of the elastic body, thus exhibiting an improved vibration damping characteristics thereof with the help of the low spring characteristics of the elastic body assured for the relatively wide load range. In addition, the load-deflection curve of the present cylindrical elastic mount has a relatively moderate slope in a relatively high load region. Thus, the present cylindrical elastic mount makes it possible to restrict an amount of axial displacement of the inner shaft member and the outer sleeve member relative to each other in a shock-absorbing manner, effectively.
In order to tune the spring characteristics or spring ratio (spring constant in a first diametric direction/spring constant in a second diametric direction perpendicular to the first diametric direction) of the present cylindrical elastic mount, the elastic body is desirably provided with voids or recesses each extending in the axial direction between the inner shaft member and the outer sleeve member.
(2) A cylindrical elastic mount according to the above-indicated mode (1), wherein the flange portion of the inner shaft member includes a portion opposed to the flange portion of the outer sleeve member via the elastic body, and having an outer diameter larger than an inner diameter of the outer sleeve member. This arrangement ensures that the flange portion of the inner shaft member and the flange portion of the outer sleeve member are opposed to each other via the elastic body in the axial direction as well, thereby increasing the area of a compressed part of the elastic body upon application of the axial load to the cylindrical elastic mount, resulting in improved durability of the cylindrical elastic mount with respect to the axial load.
(3) A cylindrical elastic mount according to the above-indicated mode (1) or (2), wherein the tapered surfaces of the flange portions of the inner shaft member and the outer sleeve member are inclined at an angle within a range of 40xc2x0-70xc2x0 with respect to the central axis of the cylindrical elastic mount. In this mode of the invention, the part of the elastic body interposed between the tapered surfaces of the flange portions of the inner shaft member and the outer sleeve member is subjected to a compression and a shear component at a suitable ratio of the axial load applied to the cylindrical elastic mount. This arrangement allows the cylindrical elastic mount to provide both of an improved vibration damping capability with respect to the axial vibrational load and an improved stopper function for limiting the axial displacement of the inner shaft member and the outer sleeve member relative to each other, in a further effective manner.
(4) A cylindrical elastic mount according to any one of the above-indicated modes (1)-(3), wherein each of the opposite surfaces of the flange portions of the inner shaft member and the outer sleeve member has a tapered cylindrical shape so that the tapered surface of the opposite surface is formed so as to extend in a circumferential direction of the corresponding flange portion over an entire circumference of the corresponding flange portion. This arrangement effectively increase the area of the opposite surfaces of the flange portions of the inner shaft member and the outer sleeve member, making it possible for the cylindrical elastic mount to exhibit desired linear spring characteristics with respect to axial loads over a wide load range and to provide a desired moderate increase of the spring constant upon application of the relatively large vibrational load to the cylindrical elastic mount.
(5) A cylindrical elastic mount according to any one of the above-indicated modes (1)-(4), wherein the opposite surface of the flange portion of the inner shaft member has a tapered cylindrical shape so that the tapered surface is formed so as to extend in a circumferential direction over an entire circumference of the flange portion of the inner shaft member, while the flange portion of the outer sleeve member includes a plurality of inclined plate parts formed at respective circumferential positions of the flange portion so as to extend in the axially outward direction inclined to the central axis of said cylindrical elastic mount and so as to extend in a circumferential direction of said flange portion with a given circumferential length, wherein the plurality of inclined plate parts are spaced apart from one another in a circumferential direction of the flange portion of the outer sleeve member by a plurality of flat plate parts, which are integrally formed at respective circumferential portions located between adjacent ones of circumferential portions from which the plurality of inclined plates extend axially outwardly, so as to extend radially outwardly, and wherein the plurality of inclined plate parts cooperate to form the tapered surface of the outer sleeve member, which is opposed to the opposite surface of the inner sleeve having the tapered cylindrical shape. In this mode of the invention, the flange portion of the outer sleeve member includes the plurality of flat plate parts extending in the radial direction perpendicular to the central axis of the cylindrical elastic mount. When the outer sleeve member is press-fitted into a fixing bore formed in the vibrative member, the flat plate parts are brought into abutting contact with the open-end surface of the fixing bore for thereby positioning the outer sleeve member relative to the fixing bore, effectively. Namely, a mechanism for positioning the outer sleeve member relative to the vibrative member is effectively provided by means of a stable contact of the flat plate parts extending radially outwardly of the outer sleeve member with the surface of the vibrative member. This arrangement accordingly eliminates a need for forming on the surface of the vibrative member a tapered abutting surfaces or the like for stably supporting the flange portion of the outer sleeve member.
(6) A cylindrical elastic mount according to any one of the above-indicated modes (1)-(5), wherein the flange portion of the outer sleeve member includes an inclined plate part integrally formed at least one circumferential portion thereof so as to extend in an inclined axially outward direction, and the outer sleeve member includes an annular plate part formed at an outer circumferential portion thereof so as to extend radially outwardly therefrom, and so as to be located at an axial position on the central axis of the cylindrical elastic mount, which is approximately equal to that of the inner circumferential end portion of the inclined plate part. In this mode of the invention, the outer sleeve member can be positioned relative to the vibrative member by an abutting contact of the annular plate part with the open-end face of the fixing bore of the vibrative member. Namely, a mechanism for positioning the outer sleeve member relative to the vibrative member is effectively provided by means of a stable contact of the radially outwardly extending annular plate part with the surface of the vibrative member. Like in the above-indicated mode (5), this arrangement eliminates a need for forming on the surface of the vibrative member a tapered abutting surfaces or the like for stably supporting the flange portion of the outer sleeve member, while allowing the vibrative ember to support the outer sleeve member with high strength as measured in the axial direction.
(7) A vibration isolating connector for connecting two members in a vibration isolating fashion, comprising a cylindrical elastic mount according to any one of the above-indicated modes (1)-(6), wherein the inner shaft member is adapted to be connected to one of the two members and the outer sleeve member is adapted to be connected to an other one of the two members so that the vibration isolating connector is subjected to a static load applied thereto in the axial direction so as to compressively deform the elastic body interposed between the flange portions of the inner shaft member and the outer sleeve member.
(8) A cylindrical elastic mount assembly comprising a pair of cylindrical elastic mounts each being constructed according to any one of the above-indicated modes (1)-(7), wherein the pair of cylindrical elastic mounts are fixedly connected to each other such that the inner shaft members fixedly connected with each other with other ones of the axially opposite ends thereof remote from the flange portions being opposed to each other, and the outer sleeve members are fixedly connected with each other with other ones of said axially opposite ends thereof remote from the flange portions being opposed to each other, and wherein the elastic body of each of the pair of cylindrical elastic mounts is held under an axial compressive force between the flange portions of the inner shaft member and the outer sleeve member.
In the vibration isolating connector according to the above-indicated mode (7) and the cylindrical elastic mount assembly according to the above-indicated mode (8), the elastic body of each of the cylindrical elastic mount is held under the axial compressive force, i.e., is pre-compressed, making it possible to enhance anti-load capacity and durability of the elastic body and the cylindrical elastic mount.